Interpretdl

InterpretDL version 0.2.3 includes improvements as follows:

- fix gradient computation issue for large models
- add LRP algorithm
- add Rollout algorithm
- update heatmap normalization method
- other small updates

Improvements

InterpretDL version 0.2.2 includes improvements as follows:
- Unify and simplify visualization methods.
- Support PaddlePaddle 2.0+ and simplify the code of loading paddle models.
- Use consistent APIs for the interpretation algorithms.
- Remove unnecessary imports.
- Add tqdm for the process bar.
- Other small modifications.

The release of InterpretDL version v0.1.8-beta based on Paddle1.8.